Star

Stars were astronomical objects large enough to sustain thermonuclear fusion within them. Due to this, stars radiated huge amounts of energy and shone incredibly bright. Stars were incredibly common, with over 400 billion of them existing in the Skyriver Galaxy alone.

Stars formed from vast clouds of matter, and often created protoplanetary disks during and after their formation, giving rise to planets, and thus creating star systems.

Objects that did not have enough mass to become stars became brown dwarfs.

Evolution
Stars died when they ran out of hydrogen to fuse. Smaller stars faded away over trillions of years, whilst moderately large ones became red giants after several billion years, eventually giving rise to white dwarfs.

Massive stars exploded as supernovae, giving rise to neutron stars, whilst the very largest stars exploded as gamma ray bursts and gave rise to black holes.

Huge groups of stars came together through the power of gravity to form star clusters and galaxies.

Classification
Stars were classified based on their mass, and thus their brightness. The largest and heaviest stars released millions of times more energy than their smaller cousins.

O-class
These were the largest and brightest stars with masses in excess of 16 SSM, radiating bright blue and ultraviolet light. They had surface temperatures of over 33,000°C, and lived for only a few million years before exploding as gamma ray bursts and producing black holes.

B-class
These stars ranged in mass from 5 to 16 SSM. Stars in this category were white-blue and hot, and had a lifespan on the order of 10 million years. They had surface temperatures of between 10,000°C and 33,000°C. They died in supernovae and mostly became neutron stars.

A-class
These stars ranged in mass from 2 to 5 SSM and radiated white light. They had lifespans of up to 2 billion years. Their surface temperatures were between 7,000°C and 10,000°C. These stars generally did not produce supernovae upon death, instead producing planetary nebulae and white dwarfs.

F-class
These stars ranged in size from 1.5 to 2 SSM and radiated yellow-white light. They had lifespans of up to 4 billion years. They had surface temperatures of 6000°C to 7000°C. These stars produced planetary nebulae and white dwarfs upon death.

G-class
These stars were often known as suns due to their relative stability and the abundance of life on planets surrounding them. They ranged in size from 0.8 to 1.5 SSM, and they averaged about 1 SSM. Indeed, G-class stars were the basis of that measurement. These stars had surface temperatures between 5000°C and 6000°C, and lived for up to 10 billion years. These stars produced planetary nebulae upon death. They radiated yellow light.

K-class
These stars ranged in size from 0.4 to 0.8 SSM. They had surface temperatures between 4000°C and 5000°C, and radiated orange light. They commonly lived for 30 billion years, although some lived to be 100 billion years old. Some of these stars produced planetary nebulae, although others faded away very slowly.

M-class
These were the smallest, dimmest and most abundant stars in the Galaxy, commonly known as red dwarfs. They had masses between 0.075 to 0.4 SSM. They had surface temperatures between 2000°C and 4000°C. These stars had immensely long lifespans, and it was believed they could burn for trillions of years. No red dwarfs had died by the time of the Galactic Republic. It was believed the red dwarfs faded away quietly at the end of their lives.